With these principles in mind, the Court denies Plaintiffs’ motion because they waited too long to amend their complaint. Plaintiffs knew or should have known the facts underlying an Establishment Clause claim when they filed their amended complaint nearly a year ago. And Plaintiffs undoubtedly knew about the Establishment Clause claim by May 31, 2012, because on that date they filed a memorandum stating that “[d]efendants’ denial of the [tribe’s] permit application creates Establishment Clause problems.” Pls.’ Mem. 14 n.19, ECF No. 30. Yet Plaintiffs waited over eight months from the time they clearly knew about the Establishment Clause claim to file the present motion. That’s simply too long a wait. The Court therefore DENIES Plaintiffs’ motion for leave to amend their complaint (ECF No. 59) based on undue delay.